Glucosinolate composition of Colombian accessions of mashua (Tropaeolum tuberosum Ruiz & Pavon), structural elucidation of the predominant glucosinolate and assessment of its antifungal activity

BACKGROUND: The content of individual and total glucosinolates in 65 mashua tuber accessions (Tropaeolum tuberosum) from the germplasm bank at Universidad Nacional de Colombia was determined by reverse phase high-performance liquid chromatography on enzymatically desulfated extracts. The predominant glucosinolate was identified and the possible structure of the glucosinolate present in lower proportion was postulated from evidence obtained by high-performance liquid chromatography/mass spectrometry, H-1 and C-13 nuclear magnetic resonance and bi-dimensional experiments. The biological action of the hydrolysis products generated fromthe glucosinolates in the accessions that showed a higher content of these compounds was assessed in the presence of Fusarium oxysporum f.sp. dianthi, Rhizoctonia solani and Phytophthora infestans. RESULTS: The total content of glucosinolates ranged between >3.00x10(-1) and 25.8 mu mol g(-1) dry matter. p-Methoxybenzyl glucosinolate was identified as the predominant glucosinolate in Colombian mashua accessions; besides, the possible presence of p-hydroxybenzyl glucosinolate was postulated. In vitro assays established an important fungal growth inhibition of the potato pathogen P. infestans. CONCLUSION: The biological action from p-methoxybenzyl glucosinolate and p-hydroxybenzyl glucosinolate found in Colombian mashua accessions depends on their concentration, with the Tt30 accession, characterized for showing the highest content of glucosinolates, being the most promising to control the assessed pathogens. (C) 2016 Society of Chemical Industry